work around webpack eval-source-map bug

Author: yyx990803

lib/parser.js

@@ -76,7 +76,10 @@ module.exports = function (content) {
       result =
         commentScript(content.slice(0, start), lang) +
         content.slice(start, end) +
-        commentScript(content.slice(end), lang)
+        commentScript(content.slice(end), lang) +
+        // workaround for Webpack eval-source-map bug
+        // https://github.com/webpack/webpack/pull/1816
+        '\n/* generated by vue-loader */\n'
     } else {
       result = content.slice(start, end).trim()
     }